Paramagnetic rim lesions are associated with choroid plexus inflammation and expansion over 5 years in people with multiple sclerosis.

Background: Chronic active white matter inflammation is linked with multiple sclerosis (MS) clinical severity and is likely integral in MS progression. It has also been associated with choroid plexus (CP) inflammation in vivo, pointing to a potential pathophysiological link between the two phenomena. However, how these aspects of the disease co-evolve over time remains poorly understood nor has their relationship been specifically assessed in people with progressive MS (pwPMS).

Methods: In this retrospective analysis of a longitudinal study, 129 people with MS (pwMS; 86 people with relapsing remitting (pwRRMS) and 43 pwPMS) were imaged with 3 T MRI at baseline and after 5.4 years of follow-up. CP volume and CP pseudo-T2 (pT2) were calculated as measures reflecting CP inflammation in MS. Paramagnetic rim lesions (PRLs), a marker of chronic active white matter inflammation, were assessed at baseline for the whole cohort, and longitudinally in 96 pwMS with available data (66 pwRRMS, 32 pwPMS). Baseline and longitudinal associations between the CP and PRLs, including interactions with disease course, were assessed, adjusted for covariates including age and sex.

Results: PwMS with PRLs had significantly larger CP volume at baseline than pwMS without PRLs after correcting for age, sex, and disease duration (mean difference: 0.3 ± 1.2 mL; p = 0.042). Longitudinally, baseline PRL number was associated with increased CP volume in pwPMS (B = 0.22 mL/mL; p < 0.001), but not people with relapsing-remitting MS (B = - 0.01 mL/mL; p > 0.7).

Conclusion: Increased CP volume is related to chronic white matter inflammation, particularly in pwPMS.